Lesson 15 of 25

The Power of the Negative Command

Naming what you do not want removes a whole class of wrong answers at once - the slang, the tourism paragraph, the mention of flooding. It works best paired with the positive instruction, because "do not do X" leaves the model to guess what to do instead. The strongest version of this technique is a ban plus a replacement: not "avoid jargon" but "no jargon - say what it does for the reader instead".

Reach for it whenWhen you keep getting the same unwanted element - the same filler phrase, the same irrelevant section, the same cheerful tone - no matter how you rephrase the request.

Put the bans in their own clearly headed section and pair each with what to do instead, then ask it to check its own output against the list before presenting it. Standing bans - words you never want, formats you always hate - belong in Custom Instructions rather than in every prompt, which is the real efficiency gain on this platform.

Worth knowingA long ban list can produce stilted writing, because the model is steering away from words rather than towards a voice. If the output reads oddly, cut the list to the three bans that matter and describe the voice you do want instead. One more thing: never rely on a negative constraint for anything consequential - "do not mention the lawsuit" is a request, not a guarantee, so read the output before it goes out.
  • Pair every ban with what to do instead.
  • Ask it to audit its own draft against the ban list.
  • Put standing bans in Custom Instructions, not every prompt.
  • Three good bans beat fifteen; too many flatten the writing.
  • Never trust a ban for anything consequential - read it yourself.
Example 1: Sculpting a Professional Tone

Instead of

Write an email to a client who has missed a payment deadline.

Perplexity version

Draft a professional email to a client whose payment is 15 days overdue. Firm but polite. The goal is to get a payment date, not to win an argument - this is a client I want to keep working with.

## DO NOT

- **No emotional or accusatory language.** Nothing that assigns blame or implies bad faith. No "you have failed to", no "we are disappointed", no "as you are well aware". Instead: state the facts and the ask in a neutral register.
- **No informalities, slang or contractions.** Write "do not" rather than "don't". Instead of a casual tone, use plain professional English - formal is not the same as stiff.
- **No passive-aggression.** This is the real failure mode here and it hides inside polite wording. "Just following up again", "I'm sure this is an oversight", "per my previous email", "gentle reminder" - all banned. Instead: say directly what is outstanding and what you are asking for.
- **No threats, and no hints of threats.** Nothing about legal action, late fees, suspending work or escalation. Instead: make the ask clear enough that it does not need a consequence attached.
- **No over-apologising.** Do not apologise for sending the email or for the inconvenience of being owed money. Instead: be courteous without being deferential.

## DO

- Open with the specific invoice: number, amount, original due date.
- One short line acknowledging that invoices get missed, without excusing it.
- A direct ask: a date by which payment will be made, or a reply saying when it will be.
- A line offering to resolve anything that is blocking it - a missing purchase order, a wrong detail on the invoice. Often that is the actual reason.
- Subject line, and keep the body under 150 words.

## THEN CHECK YOUR OWN DRAFT

Under "Ban check", go back through the email and quote any phrase that comes close to anything on the DO NOT list, including passive-aggression you did not intend. Then give me one line on how this would read to someone who is late because they are having cash flow trouble - that is the most likely reason, and I do not want the email to make an awkward situation worse.

Use [INVOICE NUMBER], [AMOUNT] and [DUE DATE] as placeholders. Do not invent any of them.
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Example 2: Carving Out Irrelevant Information

Instead of

Compare Hyderabad and Bangalore as cities for a tech startup.

Perplexity version

Create a comparison table for a tech entrepreneur deciding between Hyderabad and Bangalore as their startup headquarters.

## ROWS

At minimum: Office Space Cost, Talent Pool Availability, Government Incentives. Add rows only if they are strictly business factors - commute time's effect on working hours, startup ecosystem density, airport connectivity for client travel. If you add a row, say in one line why it affects the decision.

## DO NOT INCLUDE

- **No tourism, nightlife, food or general lifestyle.** Not as rows, not as asides in a business row, not in the summary. This is the entire point of the prompt - comparisons of these two cities are overwhelmingly lifestyle content and I need the business version. Instead: if a row genuinely has a business consequence that looks lifestyle-adjacent, state the business consequence only.
- **No "quality of life" row.** It is lifestyle wearing a business suit.
- **No weather.** Unless you are telling me about data centre cooling costs, in which case say that explicitly.
- **No city-pride language.** No "vibrant", no "Silicon Valley of India", no "up-and-coming". Instead: state what is measurable.
- **No invented figures.** Do not give me a rupees-per-square-foot number or a headcount from memory as though it were sourced. Instead: describe the relative position - "generally lower", "comparable" - and in a separate column name the source I should check for the real figure.

## FORMAT

A table: factor, Hyderabad, Bangalore, and a fourth column "Where to verify this" naming the specific source - a state IT department, a commercial property consultancy's published report, a government scheme page.

## AFTER THE TABLE

1. "Which factor should decide it" - of all the rows, which one actually determines the answer for most early-stage companies, and why. A table treats every row as equal weight, and they are not.
2. "What this table cannot tell you" - the business factors that do not fit a table at all: your own network, where your first customers are, where your co-founder lives.
3. "Lifestyle check" - confirm that nothing lifestyle-related made it in, and quote anything borderline.

Say plainly if any figures or schemes you mention may be out of date. Government incentive schemes change and an expired scheme stated confidently is worse than no answer.
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Example 3: Removing Undesired Creative Elements

Instead of

Write a short poem about the monsoon in Hyderabad.

Perplexity version

Write a four-stanza poem about the arrival of the monsoon in Hyderabad.

## WHAT THE POEM IS ABOUT

The relief when the first rain comes after the long heat. The smell of the earth - petrichor. The green that follows within days. The mood is positive and celebratory throughout, and it should stay there.

## DO NOT

- **No traffic jams, flooding, waterlogging, potholes or power cuts.** Instead: the poem lives in the hour of arrival, not in the week after.
- **No turn into melancholy.** Monsoon poems default to nostalgia and loss - rain as memory, rain as grief. Not this one. Instead: keep it in the present tense and in the body - heat, then water, then green.
- **No sadness in the final stanza.** The last stanza is where a positive poem most often collapses into wistfulness. Instead: end on the green, or on a next-morning image.
- **No "pitter-patter", no "Mother Nature", no "liquid gold", no "thirsty earth" cliches.** Instead: find the one specific image - a particular surface going dark with water, a particular smell - that a reader from Hyderabad would recognise.
- **Do not name Hyderabad landmarks for atmosphere.** No Charminar, no Hussain Sagar dropped in as scenery. Instead: let the city be present through specific sensory detail rather than through monuments.
- **No rhyme scheme unless it can be held without strain.** Forced rhyme is worse than none. Instead: use free verse if the rhyme is bending the lines.

## THEN, SEPARATELY

Under "Ban check", quote any line that drifted toward the negative, the melancholic or the cliched, including anything you caught and fixed - I want to know where the pull was. The constraint to keep a monsoon poem entirely positive works against almost every monsoon poem ever written, and where it strained is the interesting information.

Then one line: if the ban on the difficult side of the monsoon makes the poem feel less true, say so. I may decide the honest version is the better poem.
Open Perplexity 1,955 characters